The present invention relates to an actuator arrangement for a drive train, in particular a motor vehicle drive train, which has at least one friction clutch for transmitting drive torque and has a transmission, in particular a step-change transmission, wherein the friction clutch can be actuated by means of a hydraulic clutch cylinder, which is connected directly to a pump port of a pump driven by electric motor in order to actuate the friction clutch, such that the friction clutch can be actuated by varying the speed of the pump, and having a parking lock actuator device for actuating a parking lock arrangement of the drive train.
The present invention furthermore relates to a drive train having a friction clutch, a parking lock arrangement and an actuator arrangement of the abovementioned type.
Drive trains of this kind are known, for example, in the form of automatic shift transmissions or in the form of double-clutch transmissions and converter-type automatic transmissions. In this kind of automated drive train, operating elements of the drive train are actuated in an automated manner by means of suitable actuator arrangements, which can be of a hydraulic, pneumatic, electric-motor or electromagnetic kind, for example.
Hydraulic actuator arrangements of this kind are generally constructed in such a way that a pressure control valve is connected to the pressure output of a pump, by means of which valve a substantially constant line pressure is produced on the delivery side of the pump. Actuating pressures for the individual operating elements are then derived from said line pressure by means of further pressure control valves and/or directional control valves. In this case, the pump is often coupled to a drive motor of the drive train.
EP 1 236 918 B1, which defines the type in question, discloses an actuator arrangement for a wet multiplate clutch in which a pressure port of a pump driven by an electric motor is connected directly, i.e. without interposition of a pressure control valve, to a port of a hydraulic cylinder for actuating the friction clutch. In this kind of actuator arrangement, the pressure in the hydraulic cylinder and hence the actuating force or actuating travel of the friction clutch is controlled by means of the speed of the pump. On the one hand, actuator arrangements of this kind have the advantage that the pump and the electric motor can be arranged remote from the hydraulic cylinder, giving potential advantages in terms of installation space. Moreover, it is possible by means of an actuator arrangement of this kind to produce a similar control quality to that in the hydraulic circuits described at the outset, in which a line pressure is initially produced. Finally, it is advantageous that the actuator arrangement can be operated independently of the operating state of the drive motor (internal combustion engine). This kind of actuator arrangement is therefore also suitable, in particular, for hybrid drive trains or electric vehicles.
In automated vehicle transmissions, a “standstill management system” is generally required. For this purpose, conventional vehicles with manual transmission have a handbrake, which is obligatory in all vehicles. In the case of vehicles with manual transmission, the vehicle can furthermore hold itself if a gear is selected since the clutch between the transmission and the internal combustion engine is normally closed. Converter-type automatic transmissions always have an additional parking lock. In automated shift transmissions or double-clutch transmissions too, especially if the friction clutch(es) is (are) normally open, a parking lock is generally required. The parking lock can be actuated purely mechanically by the driver via an operating element (P position of the gear lever). It is furthermore possible for the parking lock to be actuated by pushbutton (park by wire) or automatically when the engine stops. In the latter case, a corresponding actuating mechanism is required in the transmission for the actuation of the parking lock.
A parking lock arrangement which is actuated by hydraulic cylinders is known from DE 10 2006 022 963 A1, for example. Where conventional hydraulic circuits, in which a pump driven by an internal combustion engine produces a line pressure, are used, however, it is not possible to guarantee the actuation of such a parking lock arrangement under all operating conditions.